The present invention relates to a thrust generator and a disk brake using the thrust generator.
There has heretofore been a disk brake for a vehicle that propels a piston to press a brake pad against a disk to apply braking force to the vehicle by using a thrust generator that converts rotational force input thereto from an electric motor or the like into rectilinear motion through a ball-and-ramp mechanism, as disclosed in Japanese Patent Application Publication No. 2002-13568.
The disk brake disclosed in Japanese Patent Application Publication No. 2002-13568 suffers, however, from the following drawback. The ball-and-ramp mechanism has a pair of ramp members with sloped grooves and a spherical member interposed between each pair of mutually opposing sloped grooves. Each sloped groove is formed such that the curvature radius of the diametrical cross-section of the groove is constant along the circumferential direction throughout a track area where the spherical member contacts the sloped groove. Therefore, durability is undesirably degraded in specific regions of the sloped groove.